406 N. E. McINDOO 



and Orthoptera; also in one coleopterous larva and in thirty spe- 

 cies of lepidopterous larvae. All of these orders, except Orthop- 

 tera, have complete metamorphoses, and consequently it was 

 more convenient to study the olfactory pores in the adult forms 

 than to use both immature and mature forms at the same time; 

 but in regard to insects having incomplete metamorphoses, it 

 is expedient to use all instars of at least one insect in the same 

 study. For this reason and in order to determine what effect 

 metamorphosis has on the olfactory pores, a careful study of the 

 disposition of these organs in all six instars of a certain grass- 

 hopper has been made. 



The two chief objects of the present investigation are: 1) to 

 determine whether the olfactory pores are better adapted ana- 

 tomically to receive olfactory stimuli than are the so-called ol- 

 factory organs on the antennae, and 2) to ascertain experimen- 

 tally the effects on the olfactory sense when the so-called olfac- 

 tory organs on the antennae are removed. 



To obtain material for the study of the disposition of the ol- 

 factory pores, dried museum specimens were mostly used; these 

 were obtained of Mr. A. N. Caudell, who also kindly identified 

 all of the species used in this study. Fresh material was fixed 

 in the modified Carnoy's fluid, and was embedded in celloidin 

 and paraffin. The sections were cut 5^ in thickness, and were 

 stained in Ehrlich's hematoxylin and eosin. All the drawings 

 were made by the writer and all are original, except figures 90 

 to 92; these represent the so-called olfactory organs (pit pegs) 

 and pegs on the antenna of a grasshopper (Tryxalis nasuta L.), 

 and were copied from Rohler ('05). The drawings were made 

 at the base of the microscope with the aid of a camera lucida. 



